Grate lock



FIG. 1 is a reduced perspective view of a grate lock showing my new design, the stove shown in broken lines is for illustrative purposes only and forms no part of the claimed design;

FIG. 2 is a top, front and left side perspective view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a right side elevational view thereof;

FIG. 7 is a rear elevational view thereof; and,

FIG. 8 is a top plan view thereof. 

The ornamental design for a grate lock, as shown and described. 